Rxjava Android how to use the Zip operator

Zip operator strictly pairs emitted items from observables. It waits for both (or more) items to arrive then merges them. So yes this would be suitable for your needs.

I would use Func2 to chain the result from the first two observables. Notice this approach would be simpler if you use Retrofit since its api interface may return an observable. Otherwise you would need to create your own observable.

// assuming each observable returns response in the form of String
Observable<String> movOb = Observable.create(...);
// if you use Retrofit
Observable<String> picOb = RetrofitApiManager.getService().uploadPic(...),
Observable.zip(movOb, picOb, new Func2<String, String, MyResult>() {
      @Override
      public MyResult call(String movieUploadResponse, String picUploadResponse) {
          // analyze both responses, upload them to another server
          // and return this method with a MyResult type
          return myResult;
      }
   }
)
// continue chaining this observable with subscriber
// or use it for something else

A small example:

val observableOne = Observable.just("Hello", "World")
val observableTwo = Observable.just("Bye", "Friends")
val zipper = BiFunction<String, String, String> { first, second -> "$first - $second" }
Observable.zip(observableOne, observableTwo, zipper)
  .subscribe { println(it) }

This will print:

Hello - Bye
World - Friends

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In BiFunction<String, String, String> the first String the type of the first observable, the second String is the type of the second observable, the third String represents the type of the return of your zipper function.

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I made a small example that calls two real endpoints using zip in this blog post